Engineers, scientists, and photographers often require electro-optical instrumentation systems that can capture images during high-speed random or catastrophic events, and produce the resulting data in minutes or even seconds. Examples of such events are explosive tests and material stress tests where the time of explosion or failure is not predictable. Near real-time playback of the recorded data is often needed to verify that the instrumentation set up is adequate.
High-speed film cameras can capture high-speed events if a pre-event trigger is available to allow the camera to ramp up to speed before the crucial event takes place, but the film must be developed and further processed in order to obtain any data. The common technique for recording these events with high-speed film cameras is to attempt to start the recording before the event occurs and to record long enough to capture the event. Since 10,000 frames-per-second film cameras can record for less than 5 seconds, this technique does not permit recording events with uncertainty in occurrence time.
High-speed video cameras are available that can collect images at frame rates up to 2,000 frames per second, and partial frames up to 12,000 segments per second but also require external triggers. These video cameras do not process the images on the fly for automatic event triggering and the storage medium is nonstandard video tape of limited length. The equipment requires a large amount of space.
A patent of interest for its teaching in this area to Cooper, U.S. Pat. No. 4,789,894, discloses a motion analyzer which records scene information at a high frame rate and plays back such information at a slower frame rate, thereby allowing slow motion analysis of a moving object. Full frames of video information from two video imagers are recorded in interleaved fashion on magnetic tape. The device is stated to have a recording frame rate of 30 to 1,000 frames per second. In the background discussion a Kodak SP2000 Motion Analysis System is discussed having a frame rate of 60 to 2,000 frames per second.
A further patent of interest to Bixby, U.S. Pat. No. 4,322,752, discloses area image sensor apparatus and methods for readout of solid-state image sensors at fast frame rates. In a preferred embodiment where photosites are arranged in rows and columns, the sensor is read out in "blocks" of photosites, with each block being comprised of a plurality of adjacent photosite rows. A block of photosites is enabled by the application of an enablement signal to the photosites within the block; and a column address signal is sequentially applied to the photosite columns to effect column-wise readout of the photosite rows within the enabled block. The output signal so produced is, therefore, comprised of block information in a "serial" format, while the information content of each block is comprised of a plurality of line signals in a "parallel" format, such line signals corresponding to the individual photosite rows within that block. Other block readable sensors are disclosed in patents to Lee et al, U.S. Pat. No. 4,322,638 and to Anagnostopoulos et al, U.S. Pat. No. 4,330,796.
A further patent of interest to Colles et al, U.S. Pat. No. 4,496,995 discloses a fast frame recorder apparatus for providing slow motion replay.
A further patent of interest to Lewis, U.S. Pat. No. 4,855,943, discloses an electronic camera for electronically recording and displaying a plurality of images, having a selection feature for proofing the images of each display frame to retain only those images desired by the photographer. One embodiment provides an imaging means of one or more displays for forming an image from an optical scene. A converter coupled to the imager converts the image into digital signals. Associated with each display device is a selecting means for selecting the image associated with the device for more permanent storage in a larger addressable memory. An optional transmitting feature unloads selected images from the addressable memory for transmission to a viewer or printer. The invention described provides for proofing, viewing, storing, a plurality of still pictures simultaneously.
A further patent of interest to Zoeller et al, U.S. Pat. No. 4,752,897, discloses a system for the monitoring and analysis of large amounts of data, and particularly to a web defect detection and analysis system. A continuous process is monitored using digital signal processing to provide a continuous flow of first digitized signals. Means are provided continuously and in parallel upon the first digital signals for reducing the first digital signals into a continuous flow of second digital signals occurring at a reduced rate from the rate of flow of the first digitized signals. These second digital signals represent predetermined events in the process, such as critical parameters and defects in a web, when the process is the production of webs of high quality. Finally, means are provided which are responsive to and operative continuously upon the second digital signals for providing outputs representing the analysis of certain effects in the process represented by the events, for example outputs representing statistical quality control information as to the categories location and even the source of the events (e.g. the defects or imperfections in the web).
The present invention comprises a solid state high-speed video camera with automatic event detection and recording of images for playback of selected images within minutes of the event. For example, a prototype has been developed which operates at up to 12,000 frames per second, detects events asynchronously, stores 4,096 images for each event and displays selected images on a PC computer system. These and other advantages of the invention will be evident from the more detailed description herein of the method and apparatus of this invention. Additional details are contained in the Appendix including a report entitled "High-Speed, Video Camera/Event Detector/Recording System".